/*
 * Submitted by David Pacheco (dp.spambait@gmail.com)
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY SUN MICROSYSTEMS, INC. ``AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL SUN MICROSYSTEMS, INC. BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/*
 * Copyright (c) 2007 Sun Microsystems. All rights reserved.
 * Use is subject to license terms.
 */

/*
 * evport.c: event backend using Solaris 10 event ports. See port_create(3C).
 * This implementation is loosely modeled after the one used for select(2) (in
 * select.c).
 *
 * The outstanding events are tracked in a data structure called evport_data.
 * Each entry in the ed_fds array corresponds to a file descriptor, and contains
 * pointers to the read and write events that correspond to that fd. (That is,
 * when the file is readable, the "read" event should handle it, etc.)
 *
 * evport_add and evport_del update this data structure. evport_dispatch uses it
 * to determine where to callback when an event occurs (which it gets from
 * port_getn).
 *
 * Helper functions are used: grow() grows the file descriptor array as
 * necessary when large fd's come in. reassociate() takes care of maintaining
 * the proper file-descriptor/event-port associations.
 *
 * As in the select(2) implementation, signals are handled by evsignal.
 */

#ifndef HAVE_CONFIG_H
#include <config.h>
#endif

#include <sys/time.h>
#include <assert.h>
#include <sys/queue.h>
#include <errno.h>
#include <poll.h>
#include <port.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
#ifdef CHECK_INVARIANTS
#include <assert.h>
#endif

#include <event.h>
#include <event-internal.h>
#include <log.h>
#include <evsignal.h>


/*
 * Default value for ed_nevents, which is the maximum file descriptor number we
 * can handle. If an event comes in for a file descriptor F > nevents, we will
 * grow the array of file descriptors, doubling its size.
 */
#define DEFAULT_NFDS	16


/*
 * EVENTS_PER_GETN is the maximum number of events to retrieve from port_getn on
 * any particular call. You can speed things up by increasing this, but it will
 * (obviously) require more memory.
 */
#define EVENTS_PER_GETN 8

/*
 * Per-file-descriptor information about what events we're subscribed to. These
 * fields are NULL if no event is subscribed to either of them.
 */

struct fd_info
  {

    struct event* fdi_revt; /* the event responsible for the "read"  */

    struct event* fdi_wevt; /* the event responsible for the "write" */
  };

#define FDI_HAS_READ(fdi)  ((fdi)->fdi_revt != NULL)
#define FDI_HAS_WRITE(fdi) ((fdi)->fdi_wevt != NULL)
#define FDI_HAS_EVENTS(fdi) (FDI_HAS_READ(fdi) || FDI_HAS_WRITE(fdi))
#define FDI_TO_SYSEVENTS(fdi) (FDI_HAS_READ(fdi) ? POLLIN : 0) | \
  (FDI_HAS_WRITE(fdi) ? POLLOUT : 0)

struct evport_data
  {
    int 		ed_port;	/* event port for system events  */
    int		ed_nevents;	/* number of allocated fdi's 	 */

    struct fd_info *ed_fds;		/* allocated fdi table 		 */
    /* fdi's that we need to reassoc */
    int ed_pending[EVENTS_PER_GETN]; /* fd's with pending events */
  };

static void*	evport_init	(struct event_base *);
static int 	evport_add	(void *, struct event *);
static int 	evport_del	(void *, struct event *);
static int 	evport_dispatch	(struct event_base *, void *, struct timeval *);
static void	evport_dealloc	(struct event_base *, void *);

const struct eventop evportops =
  {
    "event ports",
    evport_init,
    evport_add,
    evport_del,
    evport_dispatch,
    evport_dealloc,
    1 /* need reinit */
  };

/*
 * Initialize the event port implementation.
 */

static void*
evport_init (struct event_base *base)
{

  struct evport_data *evpd;
  int i;
  /*
   * Disable event ports when this environment variable is set
   */

  if (getenv ("EVENT_NOEVPORT") )
    return (NULL);

  if (! (evpd = calloc (1, sizeof (struct evport_data) ) ) )
    return (NULL);

  if ( (evpd->ed_port = port_create() ) == -1)
    {
      free (evpd);
      return (NULL);
    }

  /*
   * Initialize file descriptor structure
   */
  evpd->ed_fds = calloc (DEFAULT_NFDS, sizeof (struct fd_info) );

  if (evpd->ed_fds == NULL)
    {
      close (evpd->ed_port);
      free (evpd);
      return (NULL);
    }

  evpd->ed_nevents = DEFAULT_NFDS;

  for (i = 0; i < EVENTS_PER_GETN; i++)
    evpd->ed_pending[i] = -1;

  evsignal_init (base);

  return (evpd);
}

#ifdef CHECK_INVARIANTS
/*
 * Checks some basic properties about the evport_data structure. Because it
 * checks all file descriptors, this function can be expensive when the maximum
 * file descriptor ever used is rather large.
 */

static void
check_evportop (struct evport_data *evpd)
{
  assert (evpd);
  assert (evpd->ed_nevents > 0);
  assert (evpd->ed_port > 0);
  assert (evpd->ed_fds > 0);

  /*
   * Verify the integrity of the fd_info struct as well as the events to
   * which it points (at least, that they're valid references and correct
   * for their position in the structure).
   */
  int i;

  for (i = 0; i < evpd->ed_nevents; ++i)
    {

      struct event 	*ev;

      struct fd_info 	*fdi;

      fdi = &evpd->ed_fds[i];

      if ( (ev = fdi->fdi_revt) != NULL)
        {
          assert (ev->ev_fd == i);
        }

      if ( (ev = fdi->fdi_wevt) != NULL)
        {
          assert (ev->ev_fd == i);
        }
    }
}

/*
 * Verifies very basic integrity of a given port_event.
 */
static void
check_event (port_event_t* pevt)
{
  /*
   * We've only registered for PORT_SOURCE_FD events. The only
   * other thing we can legitimately receive is PORT_SOURCE_ALERT,
   * but since we're not using port_alert either, we can assume
   * PORT_SOURCE_FD.
   */
  assert (pevt->portev_source == PORT_SOURCE_FD);
  assert (pevt->portev_user == NULL);
}

#else
#define check_evportop(epop)
#define check_event(pevt)
#endif /* CHECK_INVARIANTS */

/*
 * Doubles the size of the allocated file descriptor array.
 */
static int
grow (struct evport_data *epdp, int factor)
{

  struct fd_info *tmp;
  int oldsize = epdp->ed_nevents;
  int newsize = factor * oldsize;
  assert (factor > 1);

  check_evportop (epdp);

  tmp = realloc (epdp->ed_fds, sizeof (struct fd_info) * newsize);

  if (NULL == tmp)
    return -1;

  epdp->ed_fds = tmp;

  memset ( (char*) (epdp->ed_fds + oldsize), 0,
           (newsize - oldsize) *sizeof (struct fd_info) );

  epdp->ed_nevents = newsize;

  check_evportop (epdp);

  return 0;
}


/*
 * (Re)associates the given file descriptor with the event port. The OS events
 * are specified (implicitly) from the fd_info struct.
 */
static int
reassociate (struct evport_data *epdp, struct fd_info *fdip, int fd)
{
  int sysevents = FDI_TO_SYSEVENTS (fdip);

  if (sysevents != 0)
    {
      if (port_associate (epdp->ed_port, PORT_SOURCE_FD,
                          fd, sysevents, NULL) == -1)
        {
          event_warn ("port_associate");
          return (-1);
        }
    }

  check_evportop (epdp);

  return (0);
}

/*
 * Main event loop - polls port_getn for some number of events, and processes
 * them.
 */

static int
evport_dispatch (struct event_base *base, void *arg, struct timeval *tv)
{
  int i, res;

  struct evport_data *epdp = arg;
  port_event_t pevtlist[EVENTS_PER_GETN];

  /*
   * port_getn will block until it has at least nevents events. It will
   * also return how many it's given us (which may be more than we asked
   * for, as long as it's less than our maximum (EVENTS_PER_GETN)) in
   * nevents.
   */
  int nevents = 1;

  /*
   * We have to convert a struct timeval to a struct timespec
   * (only difference is nanoseconds vs. microseconds). If no time-based
   * events are active, we should wait for I/O (and tv == NULL).
   */

  struct timespec ts;

  struct timespec *ts_p = NULL;

  if (tv != NULL)
    {
      ts.tv_sec = tv->tv_sec;
      ts.tv_nsec = tv->tv_usec * 1000;
      ts_p = &ts;
    }

  /*
   * Before doing anything else, we need to reassociate the events we hit
   * last time which need reassociation. See comment at the end of the
   * loop below.
   */

  for (i = 0; i < EVENTS_PER_GETN; ++i)
    {

      struct fd_info *fdi = NULL;

      if (epdp->ed_pending[i] != -1)
        {
          fdi = & (epdp->ed_fds[epdp->ed_pending[i]]);
        }

      if (fdi != NULL && FDI_HAS_EVENTS (fdi) )
        {
          int fd = FDI_HAS_READ (fdi) ? fdi->fdi_revt->ev_fd :
                   fdi->fdi_wevt->ev_fd;
          reassociate (epdp, fdi, fd);
          epdp->ed_pending[i] = -1;
        }
    }

  if ( (res = port_getn (epdp->ed_port, pevtlist, EVENTS_PER_GETN,
                         (unsigned int *) & nevents, ts_p) ) == -1)
    {
      if (errno == EINTR || errno == EAGAIN)
        {
          evsignal_process (base);
          return (0);
        }

      else if (errno == ETIME)
        {
          if (nevents == 0)
            return (0);
        }

      else
        {
          event_warn ("port_getn");
          return (-1);
        }
    }

  else if (base->sig.evsignal_caught)
    {
      evsignal_process (base);
    }

  event_debug ( ("%s: port_getn reports %d events", __func__, nevents) );

  for (i = 0; i < nevents; ++i)
    {

      struct event *ev;

      struct fd_info *fdi;
      port_event_t *pevt = &pevtlist[i];
      int fd = (int) pevt->portev_object;

      check_evportop (epdp);
      check_event (pevt);
      epdp->ed_pending[i] = fd;

      /*
       * Figure out what kind of event it was
       * (because we have to pass this to the callback)
       */
      res = 0;

      if (pevt->portev_events & POLLIN)
        res |= EV_READ;

      if (pevt->portev_events & POLLOUT)
        res |= EV_WRITE;

      assert (epdp->ed_nevents > fd);

      fdi = & (epdp->ed_fds[fd]);

      /*
       * We now check for each of the possible events (READ
       * or WRITE).  Then, we activate the event (which will
       * cause its callback to be executed).
       */

      if ( (res & EV_READ) && ( (ev = fdi->fdi_revt) != NULL) )
        {
          event_active (ev, res, 1);
        }

      if ( (res & EV_WRITE) && ( (ev = fdi->fdi_wevt) != NULL) )
        {
          event_active (ev, res, 1);
        }
    } /* end of all events gotten */

  check_evportop (epdp);

  return (0);
}


/*
 * Adds the given event (so that you will be notified when it happens via
 * the callback function).
 */

static int
evport_add (void *arg, struct event *ev)
{

  struct evport_data *evpd = arg;

  struct fd_info *fdi;
  int factor;

  check_evportop (evpd);

  /*
   * Delegate, if it's not ours to handle.
   */

  if (ev->ev_events & EV_SIGNAL)
    return (evsignal_add (ev) );

  /*
   * If necessary, grow the file descriptor info table
   */

  factor = 1;

  while (ev->ev_fd >= factor * evpd->ed_nevents)
    factor *= 2;

  if (factor > 1)
    {
      if (-1 == grow (evpd, factor) )
        {
          return (-1);
        }
    }

  fdi = &evpd->ed_fds[ev->ev_fd];

  if (ev->ev_events & EV_READ)
    fdi->fdi_revt = ev;

  if (ev->ev_events & EV_WRITE)
    fdi->fdi_wevt = ev;

  return reassociate (evpd, fdi, ev->ev_fd);
}

/*
 * Removes the given event from the list of events to wait for.
 */

static int
evport_del (void *arg, struct event *ev)
{

  struct evport_data *evpd = arg;

  struct fd_info *fdi;
  int i;
  int associated = 1;

  check_evportop (evpd);

  /*
   * Delegate, if it's not ours to handle
   */

  if (ev->ev_events & EV_SIGNAL)
    {
      return (evsignal_del (ev) );
    }

  if (evpd->ed_nevents < ev->ev_fd)
    {
      return (-1);
    }

  for (i = 0; i < EVENTS_PER_GETN; ++i)
    {
      if (evpd->ed_pending[i] == ev->ev_fd)
        {
          associated = 0;
          break;
        }
    }

  fdi = &evpd->ed_fds[ev->ev_fd];

  if (ev->ev_events & EV_READ)
    fdi->fdi_revt = NULL;

  if (ev->ev_events & EV_WRITE)
    fdi->fdi_wevt = NULL;

  if (associated)
    {
      if (!FDI_HAS_EVENTS (fdi) &&
              port_dissociate (evpd->ed_port, PORT_SOURCE_FD,
                               ev->ev_fd) == -1)
        {
          /*
           * Ignre EBADFD error the fd could have been closed
           * before event_del() was called.
           */
          if (errno != EBADFD)
            {
              event_warn ("port_dissociate");
              return (-1);
            }
        }

      else
        {
          if (FDI_HAS_EVENTS (fdi) )
            {
              return (reassociate (evpd, fdi, ev->ev_fd) );
            }
        }
    }

  else
    {
      if (fdi->fdi_revt == NULL && fdi->fdi_wevt == NULL)
        {
          evpd->ed_pending[i] = -1;
        }
    }

  return 0;
}


static void
evport_dealloc (struct event_base *base, void *arg)
{

  struct evport_data *evpd = arg;

  evsignal_dealloc (base);

  close (evpd->ed_port);

  if (evpd->ed_fds)
    free (evpd->ed_fds);

  free (evpd);
}
